JP2019074606A - Fixing apparatus - Google Patents

Abstract

To provide a fixing apparatus having a heat transmission member in contact with a heater and a film in a longitudinal direction of the heater, while allowing for temperature increase in a non-paper passing part and offset at an end.SOLUTION: A fixing apparatus includes a cylindrical film, an elongated planar heater in contact with an inner surface of the film, and a heat transmission member having a heater contact part which is long in a longitudinal direction of the heater and in contact with the heater. The heat transmission member includes a film contact part which extends in a direction toward the film to come in contact with an inner surface of the film, in at least one of an upstream area upstream of an upstream end of the heater and a downstream area downstream of a downstream end of the heater, in a rotation direction of the film. A longitudinal end of the heater contact part extends outside beyond a longitudinal end of the film contact part on the same side.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a fixing device used in an image forming apparatus such as a copying machine, a printer, and a facsimile, which has a function of forming an image on a recording material.

  As a fixing device used in an electrophotographic image forming apparatus, a film heating type is known. This fixing device has a cylindrical fixing film, a plate-like heater in contact with the inner surface of the fixing film, and a pressure roller in contact with the outer surface of the fixing film to form a nip portion. The recording material carrying the toner image is heated while being conveyed by the nip portion, and the toner image is fixed to the recording material. The fixing device of the film heating type has an advantage that the warm-up time is short because the heat capacity of the fixing film is small, and the power consumption can be suppressed as low as possible.

  By the way, a heat conducting member having a thermal conductivity higher than that of the substrate of the heater is provided to be in contact with the surface of the heater opposite to the surface in contact with the fixing film, and the heat conducting member is brought into contact with the fixing film. An extended configuration is disclosed (Patent Document 1). In addition to the heat conduction path from the heater to the fixing film, a heat conduction path from the heater to the fixing film via the heat conduction member is formed, so that the fixing film can be efficiently heated. Further, by causing the heat conducting member to be in contact with the heater and the fixing film over the longitudinal direction of the heater and the fixing film, it is possible to suppress the non-sheet-passing portion temperature rise that occurs when the small size recording material is fixed continuously. Can.

Japanese Patent Application Publication No. 2003-257592

  However, when the heat conducting member is brought into contact with the heater and the fixing film along the longitudinal direction of the heater and the fixing film, the heat may be reduced at the end due to the heat radiation at the ends of the heat conductive member. In particular, when a wide recording material is fixed, the toner at the edge of the image may be insufficiently melted, which may cause an offset at the edge of the image (hereinafter referred to as “edge offset”).

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device capable of achieving both suppression of non-sheet-passing portion temperature rise and improvement of end portion fixability.

  An aspect of the present invention is a plate-like heater having a rotatable cylindrical film, a first surface, and a second surface opposite to the first surface, wherein the first surface And a heat conducting member having a heater contact portion which is long in the longitudinal direction of the heater and in contact with the second surface of the heater. In the fixing device for heating the toner image by the heat of the heater through the film and fixing the toner image to the recording material, the heat conducting member is upstream of the upstream end of the heater in the rotation direction of the film. A film contact portion extending in a direction approaching the film to be in contact with the inner surface of the film in at least one of the region and the region downstream of the downstream end of the heater; heater Longitudinal end portion of the contact portion is therewith characterized in that it extends to the outside than the longitudinal end portions of the film contact portion of the same side.

  According to the present invention, it is possible to provide a fixing device capable of achieving both suppression of temperature rise in non-sheet-passing portion and improvement in end portion fixability.

Schematic configuration of the image forming apparatus according to the first embodiment FIG. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment. An exploded perspective view of a film unit according to Embodiment 1 Partially cutaway front view of the fixing device according to the first embodiment (A) A schematic view of the heater, the aluminum plate, the heater holder and the like according to the first embodiment as viewed from the recording material conveyance direction. (B) a schematic view of the heater and the aluminum plate according to the first embodiment as viewed from the heater holder side. FIG. 2 is a schematic cross-sectional view of the vicinity of the nip portion of the fixing device according to the first embodiment. (A) Image of longitudinal temperature distribution of heater, fixing film and pressure roller in normal use when the fixing device according to Example 1 is used, (b) Normal use in the case of using the fixing device according to Comparative Example 1 Image of longitudinal temperature distribution of heater, fixing film and pressure roller (A) Image of longitudinal temperature distribution of heater, fixing film, pressure roller when using small size recording material in fixing device according to Example 1, (b) Small size recording material using fixing device according to Comparative Example 1 Image of the longitudinal temperature distribution of the heater, fixing film and pressure roller when using FIG. 2 is a schematic cross-sectional view of a fixing device according to Embodiment 2. (A) A schematic view of the heater, the graphite sheet, the heater holder and the like according to the second embodiment as viewed from the transport direction, and (b) a schematic view of the heater and the graphite sheet according to the second embodiment as viewed from the heater holder side (A) A schematic view of the heater, the aluminum plate, the heater holder and the like according to the third embodiment as viewed from the transport direction, (b) a schematic view of the heater and the aluminum plate according to the third embodiment as viewed from the heater holder side (A) A schematic view of the heater, the aluminum plate, the heater holder and the like according to the fourth embodiment as viewed from the transport direction, and (b) a schematic view of the heater and the aluminum plate according to the fourth embodiment as viewed from the heater holder side Schematic which looked at the heater and heat conduction member concerning the modification of this example from the heater holder side Schematic sectional view of a fixing device according to a modification of the present embodiment (A) A schematic view of the heater, the aluminum plate, the heater holder and the like according to the fifth embodiment viewed from the transport direction, (b) a schematic view of the heater and the aluminum plate according to the fifth embodiment viewed from the heater holder side, (c) the embodiment 5 is a schematic cross-sectional view of the vicinity of the nip portion of the fixing device according to 5 (A) A schematic view of the heater, the aluminum plate, the heater holder and the like according to the sixth embodiment as viewed from the transport direction, (b) a schematic view of the heater and the aluminum plate according to the sixth embodiment as viewed from the heater holder side, (c) the embodiment The figure which expanded the longitudinal edge part of the aluminum plate which concerns on 6 (A) An enlarged view of the longitudinal end of the aluminum plate according to Example 6, (b) a temperature portion of a region corresponding to the longitudinal end of the aluminum film of the fixing film, (c) a longitudinal end of the aluminum plate of the fixing film Temperature part of area corresponding to part (A) A schematic view of the heater, the aluminum plate, the heater holder and the like according to the seventh embodiment viewed from the transport direction, (b) a schematic view of the heater and the aluminum plate according to the seventh embodiment viewed from the heater holder side, (c) the embodiment The figure which expanded the longitudinal end of the aluminum plate which concerns on 7 The figure which expanded the longitudinal edge part of the aluminum plate which concerns on the modification of Example 7

Example 1
First, the main configuration of the image forming apparatus according to the present embodiment will be described, and then, the fixing device according to the present embodiment will be described in detail.

(1) Image Forming Apparatus The configuration of the image forming apparatus according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a general color image forming apparatus (in the present embodiment, an electrophotographic intermediate transfer full-color printer) according to a first embodiment of the present invention.

  The color image forming apparatus includes four image forming units 1Y, 1M, 1C, and 1Bk that form yellow, magenta, cyan, and black images, respectively. These four image forming units are arranged in a line at a constant interval.

  Photosensitive drums 2a, 2b, 2c and 2d as image bearing members are installed in the respective image forming portions 1Y, 1M, 1C and 1Bk. Around the photosensitive drums 2a, 2b, 2c and 2d, charging rollers 3a, 3b, 3c and 3d, developing devices 4a, 4b, 4c and 4d, transfer sheets 5a, 5b, 5c and 5d, and a drum cleaning device 6a , 6b, 6c, 6d are respectively installed. Further, around the photosensitive drums 2a, 2b, 2c and 2d, exposure devices 7a, 7b and 7c, above the charging rollers 3a, 3b, 3c and 3d and the developing devices 4a, 4b, 4c and 4d, respectively. 7d is installed respectively. The developing devices 4a, 4b, 4c, and 4d respectively store yellow toner, magenta toner, cyan toner, and black toner of negative charging characteristics.

  The photosensitive drums 2a, 2b, 2c and 2d are organic photosensitive members of negative charge in this embodiment and have a photosensitive layer on an aluminum drum substrate, and are driven by a driving device (not shown) in the direction of the arrow (counterclockwise). It is rotationally driven at a predetermined process speed.

  The charging rollers 3a, 3b, 3c, and 3d are in contact with the photosensitive drums 2a, 2b, 2c, and 2d, respectively, with a predetermined pressure, and a desired charging bias is applied by a charging bias power supply (not shown). Then, the surfaces of the photosensitive drums 2a, 2b, 2c and 2d are uniformly charged to a predetermined potential. In the present embodiment, the photosensitive drums 2a, 2b, 2c and 2d are negatively charged by the charging rollers 3a, 3b, 3c and 3d.

  The exposure devices (laser scanner devices) 7a, 7b, 7c, and 7d have laser output units (laser beams modulated corresponding to time-series electric digital pixel signals of image information respectively input from a host computer (not shown)). Output from (not shown). The laser light exposes the surfaces of the photosensitive drums 2a, 2b, 2c, and 2d through the reflection mirrors (not shown). As a result, electrostatic latent images corresponding to the image information are formed on the surfaces of the photosensitive drums 2a, 2b, 2c, 2d charged by the charging rollers 3a, 3b, 3c, 3d.

  The developing devices 4a, 4b, 4c and 4d use a contact developing method as a developing method, and have a developing roller as a developer carrier. The toner carried on the thin layer on the developing roller is conveyed to a portion (developing portion) opposed to the photosensitive drums 2a, 2b, 2c and 2d by the developing roller rotated by a developing driving unit (not shown). Then, the electrostatic latent image formed on the photosensitive drum is developed (reversal development) as a toner image by a developing bias applied to a developing roller by a developing voltage applying unit (not shown).

  The developing rollers and the photosensitive drums in the developing devices 4a, 4b, 4c and 4d are in contact in the full color image forming mode, and in the mono color image forming mode to be described later The body drum is configured to be separated. This is to prevent the deterioration and consumption of the developing roller and the toner.

  The transfer sheets 5a, 5b, 5c, and 5d as sheet-like transfer means are formed of sheets made of a conductive resin. The transfer pads 15a, 15b, 15c and 15d as transfer sheet pressing members are made of an elastic body made of rubber or the like.

  The intermediate transfer belt 20 is formed in an endless belt shape from a semiconductive resin. The intermediate transfer belt 20 is stretched by a drive roller 21, a tension roller 22, and a secondary transfer opposite roller 23, tensioned by a pressing unit (not shown) against the tension roller 22, and rotationally driven by the drive roller 21. Ru.

  An intermediate transfer belt 20, which is an endless belt-like intermediate transfer member, is in contact with the photosensitive drum 2a. The transfer sheet 5a is in contact with the intermediate transfer belt 20, and further in contact with the transfer pad 15a and pressed. As a result, the transfer pad 15 a is pressed against the photosensitive drums 2 a via the transfer sheet 5 a and the intermediate transfer belt 20. The transfer sheet 5a is connected to a primary transfer power supply (not shown) as a primary transfer power supply. The toner image developed on the photosensitive drum 2a is primarily transferred onto the rotating intermediate transfer belt 20 by the transfer sheet 5a to which the primary transfer voltage is applied.

  The configuration described above is the transfer unit configuration of the image forming unit 1Y, and the same configuration is also applied to the other image forming units 1M, 1C, and 1Bk. The yellow and black toner images formed by the photosensitive drums 2c and 2d of the image forming units 1C and 1Bk are formed on the yellow and magenta toner images superimposed and transferred onto the intermediate transfer belt 20 in the same manner as the image forming unit 1Y. The respective primary transfer portions are sequentially superposed. As a result, a full color toner image is formed on the intermediate transfer belt 20.

  The secondary transfer roller 24 is pressed against the secondary transfer counter roller 23 from the outside direction of the intermediate transfer belt 20, and is configured to be able to contact and separate from the intermediate transfer belt 20. The recording material P is conveyed to a contact portion between the secondary transfer roller 24 and the intermediate transfer belt 20. A secondary transfer power supply (not shown) as a secondary transfer power supply is connected to the secondary transfer roller 24. The toner image primarily transferred onto the intermediate transfer belt 20 is secondarily transferred onto the recording material P being conveyed by a secondary transfer roller to which a secondary transfer voltage is applied.

  As a belt cleaning device for removing and collecting transfer residual toner remaining on the surface of the intermediate transfer belt 20 on the downstream side of the rotational direction of the intermediate transfer belt 20 at the contact portion between the intermediate transfer belt 20 and the secondary transfer roller 24 , The cleaning charging roller 25 is in contact. A cleaning power supply (not shown) is connected to the cleaning charging roller 25, and the transfer residual toner is removed by the cleaning charging roller 25 to which a cleaning voltage is applied.

  In addition, the sensor unit 50 for color registration correction / density correction is provided in the vicinity of the drive roller 21 in order to obtain stable color registration and image density regardless of various conditions such as changes in the environment used and the number of image formations. It is provided. The color registration correction / density correction sensor unit 50 is composed of a light emitting element such as an LED and a light receiving element such as a photodiode or CdS.

  On the downstream side of the secondary transfer roller 24 in the conveyance direction of the recording material P, a fixing device 12 having a fixing roller 43, a fixing film 30, and a pressure roller 33 is installed. Here, by conveying the recording material P between the fixing roller 43 and the pressure roller 33, at the same time, the toner image t is heated and pressed to fix it as a permanently fixed image on the surface of the recording material P.

  Further, at the time of color registration correction and density correction, a toner image is formed on the intermediate transfer belt 20, and light from the light emitting element is applied to the toner image on the intermediate transfer belt 20 which is rotationally moved and a portion without the toner image. Then, by receiving the reflected light from them by the light receiving element, the formed position and density of the toner image patch are measured. At the time of color registration correction, the color registration is corrected by measuring an interval of presence or absence of a toner image. At the time of density correction, the density is corrected by measuring the density of the toner image.

  The color image forming apparatus of this embodiment is compatible with a plurality of paper sizes, and includes a plurality of paper sizes including Letter paper (about 216 mm × 279 mm), A4 paper (210 mm × 297 mm), and A5 paper (148 mm × 210 mm). It can print. Basically, it is a printer that longitudinally feeds paper (conveys with the long side parallel to the conveyance direction), and is the largest (width) among the compatible fixed recording material sizes (corresponding paper sizes in the catalog) The size is about 216 mm width of Letter paper. As described above, in the present proposal, a sheet (A4 sheet, A5 sheet) having a sheet width smaller than the maximum size supported by the image forming apparatus is defined as a small size sheet.

(2) Fixing Device The fixing device 12 will be described. The fixing device 12 is a film heating type device. The fixing device 12 of the film heating type uses an endless belt as a heat-resistant film, and the film is rotationally driven by the rotational driving force of the pressing body.

  Hereinafter, the film heating type fixing device will be described in detail. FIG. 2 is a cross-sectional view of the fixing device of the color image forming apparatus according to the first embodiment. FIG. 3 is an exploded perspective view of a film unit used for the identification attachment device, and FIG. 4 is a partially cutaway front view of the identification attachment device.

  The heater holder 31 functions as a support member for supporting the heater 32 and guides the rotational travel of the cylindrical fixing film 30. The heater holder 31 can be suitably made of a highly heat resistant resin such as polyimide, polyamide imide, PEEK, PPS, liquid crystal polymer, or a composite material of such resin and ceramics, metal, glass or the like. Among them, a liquid crystal polymer which has a high heat resistance temperature, can be molded and is excellent in dimensional stability can be particularly preferably used. Liquid crystal polymers have the following advantages. First, since the heat resistance temperature is high, the degree of freedom of the set temperature of the heater can be increased. Moreover, since it can be molded, it has high productivity and mass production is possible. Furthermore, since the dimensional stability is excellent, it is possible to make the pressing force on the pressing member uniform and to stabilize the paper conveyance performance.

  The heater 32 has a long thin plate shape. The heater 32 is a ceramic substrate having high heat resistance (in this embodiment, alumina having a thermal conductivity of 30 W / (m · K) is used) and a resistance heating element 82 using Ag / Pd (silver-palladium) The electrodes are printed. Furthermore, a glass coat 84 is provided to protect the resistance heating element 82. The resistance heating element 82 uses two heating elements, and two electrodes are disposed on one side. A glass coat 84 layer is placed on the side that contacts the fixing film 30.

  The fixing film 30 is a member provided with an elastic layer on the outer side of an endless belt-like (cylindrical) base layer and further provided with a release layer on the outer side, and is configured to be rotatable.

  The release layer is a layer that prevents an offset phenomenon that occurs when toner once adheres to the surface of the fixing film 30 and moves to the recording material P again, and has a thickness of about 5 to 70 μm and good release properties. Fluorine resins such as PFA, PTFE and FEP can be suitably used. In this embodiment, by using a PFA tube with a thickness of 15 μm, a uniform fluorocarbon resin layer can be easily formed.

  Elastic layers are often used, particularly in fixing devices in color image forming devices. This elastic layer makes it possible to heat the toner image t in the form of wrapping the toner image t regardless of the unevenness of the surface of the recording material P, and as a result, it is possible to obtain a uniform color gloss image. In the present embodiment, a silicone rubber layer having a relatively high thermal conductivity is used as the elastic layer. As a result, higher on-demand performance and better fixing performance can be obtained.

  The base layer is a layer in contact with the heater on the innermost side of the fixing film 30. The base layer is excellent in heat resistance, and flexible polyimide, polyamide imide, PEEK or the like is used, and the base layer is formed to have a thickness of about 10 to 100 μm. In the nip portion N where the heater 32 and the pressure roller face each other, the fixing film 30 can be sufficiently in close contact with the heater so as to efficiently transfer the heat of the heater to the toner image t on the recording material P It is important to have

  In order to improve the flexibility, it is effective to make the layer thinner. On the other hand, since the fixing film 30 maintains the mechanical strength by the base layer, when the thickness of the base layer is extremely thin, the strength is reduced and the film is deformed to be easily wrinkled, and the end portion is seated. It is not possible to obtain the necessary strength such as being easy to bend. In order to prevent this, when the base layer is polyimide, the thickness needs to be 10 μm or more. In this embodiment, a cylindrical polyimide resin having a thickness of 50 μm and an inner diameter of 18 mm measured by a micrometer is used.

  The configuration of the fixing device will be described with reference to the cross-sectional view of FIG. The reinforcing member 34 is made of metal such as iron and is a member that maintains its strength so as not to be greatly deformed even by the pressure that presses the heater holder 31 to the pressure roller side. The heater 32 is pressed toward the pressure roller 33 by the pressing means described later via the heater holder 31 and the reinforcing member 34. The area pressed by the pressure roller 33 and the fixing film 30 in close contact with each other is the fixing nip N (as a pressure contact area). The pressure position of the pressure roller 33 and the position of the central portion of the heater 32 in the recording material conveyance direction are substantially the same.

  Next, it demonstrates with reference to the perspective view of FIG. The heater holder 31 has a substantially bowl-like shape in cross section, and the reinforcing member 34 is fitted inside the bowl-like shape. A heater receiving groove is provided on the side of the heater holder 31 facing the pressure roller 33, and the heater 32 is fitted in the heater receiving groove and fitted at a desired position. At this time, an aluminum plate 81 is interposed between the heater 32 and the heater receiving groove. Details of the aluminum plate 81 will be described later. Also, a thermistor (not shown) is attached to the heater holder 31, and the heater 32 and the aluminum plate 81 are disposed at a position to be in contact with the aluminum plate 81 when fitted in the heater receiving groove. The fixing film 30 is externally fitted on the outer side of the heater holder 31 on which the above-described components are assembled with a sufficient circumferential length. The axial direction of the cylindrical shape of the fixing film 30 (the arrow direction in which the fixing film is inserted in the drawing) is hereinafter referred to as the longitudinal direction. The projecting portions of the reinforcing member 34 protrude from both ends of the fixing film 30, and the flange members 36 are fitted to the both ends, respectively, and the whole is assembled as a film unit. The feed terminal of the heater 32 also protrudes from one end of the fixing film 30, and the feed connector 35 is fitted. The feed connector 35 contacts the electrode portion of the heater 32 with a contact pressure to form a feed path.

  The pressure roller 33 as a pressure roller includes a metal core, an elastic layer made of silicone rubber having elastic properties, and a release layer having releasability. A drive gear 44 is attached to one end of the cored bar of the pressure roller 33, and the pressure roller 33 is rotated by receiving a rotational drive force by a drive unit (not shown).

  Next, it demonstrates with reference to the front view of FIG. The flange member 36 regulates movement of the rotating fixing film 30 in the longitudinal direction, and regulates the position of the fixing film in operation of the fixing device. The flange of the flange member 36 (portion that regulates the end portion of the fixing film) is disposed such that the distance between the left side and the right side is longer than the longitudinal length of the fixing film 30.

  This is to prevent damage to the film edge during normal use. Further, the length of the pressure roller 33 in the longitudinal direction is shorter than that of the fixing film 30 by about 10 mm. This is to prevent the grease protruding from the end portion of the fixing film 30 from contacting with the pressure roller and losing the grip and the occurrence of the slip.

  The film unit is provided opposite to the pressure roller 33, and the movement in the lateral direction in the drawing is restricted, and the movement in the vertical direction is supported by the top plate side casing 39 of the fixing device so as to be movable. . A pressure spring 38 is attached to the top plate side housing 39 of the fixing device in a compressed state. The pressing force of the pressure spring is received by the projecting portion of the reinforcing member 34. The pressure roller 34 is pressed against the pressure roller 33, and the entire film unit is pressed toward the pressure roller. A bearing 37 is provided to pivotally support the core of the pressure roller 33. The pressure from the film unit is received by the bearing 37 via the pressure roller. In order to rotatably support the core metal of the pressure roller, which has a relatively high temperature, the material of the bearing is heat resistant, and a material having excellent slidability is used. The bearing 37 is attached to the bottom case 40 of the fixing device.

  Next, the operation of the fixing device will be described with reference to the sectional view of FIG. An aluminum plate 81 is disposed in contact with the opposite surface of the heater 32 in contact with the fixing film 30. Furthermore, a thermistor 41 which is a temperature detection element is provided in contact with the aluminum plate 81. Based on the temperature detected by the thermistor 41, the power supplied to the heater 32 is controlled by control means (not shown) to make the heater 32 have a desired temperature (target temperature).

  The pressure roller is rotationally driven by a drive unit (not shown), and the fixing film 30 is rotated by the frictional force between the pressure roller 33 and the outer surface of the fixing film 30 at the fixing nip N. Since the fixing film 30, the heater 32, and the heater holder 31 slide while being pressed, grease (lubricant) (not shown) is applied to the surface of the heater in order to reduce its frictional resistance. Grease is a heat resistant grease obtained by mixing and dispersing a fluorine oil, which is a liquid lubricant, and a fluorine resin, which is a solid lubricant, as a base. Grease is interposed between the film and the heater to maintain good slidability even for long-term use.

  As described above, the recording material P is formed by transferring the toner image t, and is conveyed between the fixing film 30 and the pressure roller 33. A guide member 42 is provided to ensure that the leading end of the recording material P is introduced into the fixing nip N. The toner image t on the recording material P is melted by receiving sufficient pressure and temperature at the fixing nip portion N, and is fixed on the recording material P as a permanently fixed image.

(3) Aluminum plate Next, the aluminum plate 81 which is the feature of this embodiment will be described in detail. As shown in the cross sectional view of FIG. 2, an aluminum plate 81 as a high thermal conductivity member is in contact with the surface (second surface) opposite to the surface (first surface) of the heater 32 in contact with the fixing film 30. ing. A groove is provided on the side of the heater holder 31 facing the pressure roller 33, and an aluminum plate 81 and a heater 32 are fitted in the heater receiving groove and supported at a desired position.

  The cross section perpendicular to the longitudinal direction of the aluminum plate 81 is such that the end portion in the short direction (recording material conveyance direction) of the aluminum plate 81 is bent in a Z shape and contacts both the heater 32 and the fixing film 30 It is provided as. With such a configuration, in addition to the heat conduction path from the first surface of the heater 32 to the fixing film 30, a heat conduction path from the heater 32 to the fixing film 30 via the aluminum plate 81 is formed. As a result, it is advantageous to cope with the speeding up where high heat transfer efficiency from the heater to the film is required.

  As the material of the aluminum plate 81, metals having high thermal conductivity such as gold, silver, copper and the like other than aluminum are preferable. It is also possible to use, as the aluminum plate 81, magnesium or nickel having good thermal conductivity, and further, for example, aluminum alloys or copper alloys of the 3000, 5000, and 6000 series mainly composed of the above metals. The heat conductive member desirably has a thermal conductivity higher than the thermal conductivity of the substrate of the heater (the thermal conductivity of the alumina serving as the base of the heater 32 is 30 W / (m · K)).

  In the present embodiment, pure aluminum (A1050) is used for the aluminum plate 81, and the thermal conductivity is 230 W / (m · K). Since the thermal conductivity is very high compared to the thermal conductivity of the heater 32, the effect of suppressing the non-sheet-passing portion temperature rise is large.

  Next, the positional relationship of the longitudinal direction of the aluminum plate 81 of a present Example is demonstrated using FIG. FIG. 5A is a view of the heater 32, the aluminum plate 81, the heater holder 31 and the like according to the present embodiment as viewed from the recording material conveyance direction. FIG. 5B is a schematic view of the heater 32 and the aluminum plate 81 as viewed from the heater holder 31 side. FIG. 5C is a schematic cross-sectional view in which the vicinity of the fixing nip portion of the fixing device is enlarged.

  As shown in FIG. 5A, in the present embodiment, after the aluminum plate 81 as the high thermal conductivity member is attached to the heater holder 31, the heater 32 is further attached. As a result, the longitudinal center of the heater 32 is supported by the heater holder 31 with the aluminum plate 81 interposed therebetween, and the longitudinal end of the heater 32 is supported by being in direct contact with the heater holder 31. The smaller the contact thermal resistance between the heater 32 and the aluminum plate 81, the better the thermal efficiency. Therefore, in the present embodiment, the above-described heat resistant grease is used in common, and the grease is interposed between the heater 32 and the aluminum plate 81.

  As shown in FIG. 5B, the substrate of the heater 32 of this embodiment is a plate-like shape having a longitudinal length of 270 mm, a short length of 6.0 mm, and a thickness of 1.0 mm. The longitudinal length of is 219 mm and forms two patterns of the same resistance. As shown in FIG. 5C, the short end of the aluminum plate 81 is bent in a Z shape so that the cross section perpendicular to the longitudinal direction has a hat shape. The portion of the aluminum plate 81 that hits the top crown of the cap is the area (portion) in contact with the heater 32. Here, this area (portion) is an area (heater contact portion) a, and the maximum length in the longitudinal direction is A. In the present embodiment, A is 218 mm. In addition, a part (the boundary between the eaves and the slip) of the part that hits the hat-shaped eaves becomes an area (a part) in contact with the fixing film. This area (portion) is an area (film contact portion) b, and the maximum length in the longitudinal direction is B. In the present embodiment, B is 214 mm. In the longitudinal direction of the aluminum plate 81, the longitudinal end of the area a of the aluminum plate 81 is outside the longitudinal end of the area b. In the present embodiment, the area (film contact portion) b of the aluminum plate 81 includes a first film contact portion provided in the area on the upstream side of the upstream end of the heater 32 in the rotation direction of the fixing film 30. Furthermore, the area (film contact portion) b of the aluminum plate 81 includes a second film contact portion provided in the area downstream of the downstream end of the heater 32 in the rotation direction of the fixing film 30. In addition, the structure provided with any one of a 1st film contact part and a 2nd film contact part may be sufficient.

(4) Effects Generally, the longer the longitudinal length of the high thermal conductivity member, the more effective the suppression of temperature rise in the non-sheet-passing area, but the heat is fixed by the heat radiation of the heater 32 or the fixing film 30 It becomes worse easily. Therefore, there is a trade-off between non-sheet temperature rise and edge fixability. By adopting the configuration of the present embodiment, it is possible to simultaneously suppress the temperature rise in the non-sheet-passing portion and improve the fixing ability at the end portion. The mechanism will be described below in the order of "the heat conduction of the aluminum plate", "the fixing ability at the end portion" and "the temperature rise at the non-sheet-passing portion".

<About heat conduction of aluminum plate>
Since the area a of the aluminum plate 81 is in contact with the heater 32 which is at a high temperature, the heater 32 serves as a heat source, and the aluminum plate 81 receives the heat. Since the area b of the aluminum plate 81 is in contact with the fixing film 30 which is at a low temperature as compared with the heater 32, the aluminum plate 81 serves as a heat supply source, and the fixing film 30 receives the heat. Thus, in addition to the supply of heat directly from the heater 32 to the fixing film 30, the heat can be supplied to the fixing film 30 via the aluminum plate 81. Since the second surface of the heater 32 is a portion where heat is likely to be accumulated in the heater 32 when the aluminum plate 81 is not present, the thermal diffusion of the heater 32 is improved by bringing the aluminum plate 81 into contact.

<On the edge fixing property>
The influence of the lengths A and B on the end fixability will be described below. FIG. 6A shows an image of the temperature distribution during normal use when the fixing device in this embodiment is used.

  First, the influence of the length A of the area a of the aluminum plate 81 on the end fixability will be described with reference to FIG. 6 (a). As described above, the heat is received from the heater 32 in the area a of the aluminum plate 81 and the heat is applied to the fixing film 30 in the area b. Therefore, as long as the area a of the aluminum plate 81 is in contact with the high temperature area (heat generation area) of the heater 32, heat can be expected to be received. The amount of heat that can be supplied from the area b to the fixing film 30 through the area a of the longitudinal end of the aluminum plate 81 in contact with the heater 32 must be supplied to the fixing film 30 from the longitudinal end of the area b of the aluminum plate 81 The end fixing property is good because there is a sufficient margin for the amount of heat to be obtained.

  Next, FIG. 6B shows an image diagram of a temperature distribution during normal use when the fixing device in the comparative example is used. Here, as a comparative example, the length B of the area b is longer than the length A of the area a of the aluminum plate 81. The influence of the length B of the area b of the aluminum plate 81 on the end fixing property will be described with reference to FIG. 6 (b). When heat is supplied from the area b of the aluminum plate 81 to the fixing film 30 and the length B of the area b is long, the longitudinal end of the area b contacts the area lower in temperature than the longitudinal center of the fixing film 30 Do. Further, the area a of the aluminum plate 81 in contact with the high temperature area (heat generation area) of the heater 32 is smaller than that of the present embodiment. As a result, the amount of heat supplied from the heater 32 to the area b through the area a of the aluminum plate 81 is not sufficient, so the amount of heat supplied to the fixing film 30 from the longitudinal end of the area b of the aluminum plate 81 is insufficient. Part fixability is likely to deteriorate. When the end fixing property is deteriorated, an image defect (end offset) in which the toner at the image end becomes insufficiently melted may occur when the wide-width recording material such as the maximum size sheet is fixed.

  From the foregoing, with regard to the end fixing property, if the length A of the area a is longer than the length B of the area b of the aluminum plate 81, the end fixing property is less likely to deteriorate.

<About the non-sheet-passing part temperature rise>
FIG. 7 (a) is an image diagram of temperature distribution at the time of small size sheet passing when the fixing device in this embodiment is used, and FIG. 7 (b) is at the small size sheet passing when the fixing device in the comparative example is used. The image figure of temperature distribution is shown. Since the heat source is the heater 32 when the non-sheet passing portion temperature rise occurs, it is preferable that the aluminum plate 81 be in direct contact with the heater. As shown in FIG. 7A, in the present embodiment, the length A of the area a of the aluminum plate 81 in contact with the heater 32 is long, and the area where the soaking effect of the heater 32 can be obtained as the length A is longer. Of the non-sheet-passing portion is high. On the other hand, in the comparative example, as shown in FIG. 7B, since the length B of the area b of the aluminum plate 81 in contact with the fixing film 30 is long, the heat accumulated in the heater 32 is fixed Since the temperature must be equalized through the film 30, the efficiency of the temperature equalizing is worse than in the present embodiment. As a result, it can be seen that the longer the length B of the area b of the aluminum plate 81, the smaller the effect of suppressing the temperature rise in the non-sheet-passing portion, but the smaller the effect.

  From the above, regarding the non-sheet-passing portion temperature rise, it is more effective to suppress the non-sheet-passing portion temperature increase by making the length A of the region a longer than the length B of the region b of the aluminum plate 81 I understand that. Assuming that the maximum longitudinal width of the contact area with the heater is A and the maximum longitudinal width of the contact area with the fixing film is B, the temperature rise of the non-sheet passing portion is suppressed by B <A. The effect of achieving both the improvement of the end portion fixing ability at a higher level can be obtained.

(5) Image output experiment result Next, the result of the image output experiment at the time of using a present Example is demonstrated.

  The following evaluations were made on the non-sheet passing portion temperature rise and the end offset. First, the evaluation of the non-sheet-passing portion temperature rise will be described. As a recording material, Canon Red Label (Canon EU, trade name) having a basis weight of 80 g / m 2 and a paper size of A4 (small-size paper) was used. With the fixing device cooled to room temperature, the maximum value of the roller surface temperature at the non-sheet-passing portion of the pressure roller 33 was measured when 1000 sheets were continuously printed.

  In consideration of the heat resistance of the pressure roller 33 (heat resistance of silicone rubber used as an elastic layer), the target is set to 230 ° C. Therefore, when it exceeds 230 degrees, it was set as x and below 230 degrees as ○.

  Next, evaluation of the end offset will be described. As a recording material, Xerox Vit aluminum Multipurpose Printer Paper Xerox Business 4200 Paper (trade name: Xerox) with a basis weight of 75 g / m 2 and a paper size of Letter (largest size paper) was used. With the fixing device cooled to room temperature, 100 consecutive images of full color RED (Y: 100% + M: 100%) were printed, the obtained image was confirmed, and the level of edge offset was ranked. . The case where no occurrence occurred was ○, the case where a slight occurrence was △, and the case where an occurrence occurred was x.

  As for the Δ level, although the occurrence is slight, the target is assumed to be ○ where no offset occurs.

  A plain paper mode is used as the printing mode, and in the image forming apparatus used in the experiment, the process speed at this time is 300 mm / sec, and the throughput is 60 sheets per minute. The atmosphere environment in which the experiment was conducted was a temperature of 23 ° C. and a humidity of 50%.

  The evaluation results are shown in Table 1. This will be described with reference to the line of the first embodiment. In the present embodiment, as described above, the length A of the area a of the aluminum plate 81 is 218 mm, and the length B of the area b is 214 mm. In the present example, no end offset occurred (O), and the non-sheet-passing portion temperature rise was 226 ° C.

  Next, the result of the image output experiment in the case of using the comparative example will be described. As a comparative example, the configuration of the image forming apparatus and the basic configuration of the fixing device are the same as in Example 1, and among them, the length of the aluminum plate 81 (maximum longitudinal width A of the contact area with the heater and fixing film The conditions which differ only in the maximum longitudinal width B) of the contact area of. In Comparative Example 1, the length A of the aluminum plate is 214 mm and the length B is 218 mm. In Comparative Example 2, the length A of the aluminum plate is 216 mm, and the length B is 216 mm. In Comparative Example 3, the length A of the aluminum plate is 214 mm and the length B is 214 mm. In Comparative Example 4, the length A of the aluminum plate is 218 mm and the length B is 218 mm.

  As an evaluation method, it evaluated using the evaluation method same as the evaluation method at the time of using a present Example. The evaluation results are as shown in Table 1. In Comparative Example 1, an end offset occurred (x), and the non-sheet-passing portion temperature rise was 236 ° C. In Comparative Example 2, the edge offset slightly occurred (Δ), and the non-sheet-passing portion temperature rise was 231 ° C. In Comparative Example 3, no end offset occurred (O), and the non-sheet-passing portion temperature rise was 242 ° C. In Comparative Example 4, the end offset occurred (x), and the non-sheet-passing portion temperature rise was 221 ° C. As compared with Comparative Examples 1 to 4, it can be seen that the present embodiment can achieve both suppression of temperature rise in the non-sheet-passing portion and improvement in the fixing ability at the end portion at a higher level.

  As described above, in the longitudinal direction of the aluminum plate, the longitudinal end of the region a of the aluminum plate is extended to the outside of the longitudinal end of the region b, thereby suppressing the temperature rise of the non-sheet passing portion It is possible to simultaneously improve the end portion fixability at a higher level.

Example 2
In this embodiment, an example in which the present invention is applied to a configuration using a graphite sheet as a high thermal conductivity member different from the aluminum plate used in the first embodiment will be described. The configuration of the image forming apparatus is the same as that of the first embodiment, as shown in FIG. Therefore, duplicate explanations are omitted.

  FIG. 8 is a cross-sectional view of the fixing device of the color image forming apparatus according to the second embodiment. The description overlapping with that of the first embodiment is omitted. The difference from the first embodiment is that the graphite sheet 83 is used instead of the aluminum plate 81. The graphite sheet 83 has a structure in which carbon crystallized in two dimensions is laminated in a sheet shape, and is a material having a very high thermal conductivity in the sheet surface. As shown in FIG. 8, a graphite sheet 83 as a high thermal conductivity member is provided on the back surface of the heater 32. A groove is provided on the side of the heater holder 31 facing the pressure roller 33 as in the first embodiment, and the heater 32 is fitted in the groove and supported at a desired position. At this time, the graphite sheet 83 is interposed between the heater 32 and the heater receiving groove. The graphite sheet 83 is bent so as to have a hat-shaped cross section, and is in contact with the heater 32 and also in contact with the rotating fixing film 30. Both ends of the cross section of the graphite sheet 83 (the tip of the eaves of a hat) are held by being held by the heater holder 31.

  The positional relationship of the graphite sheet 83 as the high thermal conductivity member of the present embodiment will be described with reference to FIG. FIG. 9A is a view of the heater 32, the graphite sheet 83, the heater holder 31 and the like according to the present embodiment as viewed from the recording material conveyance direction. FIG. 9B is a schematic view of the heater 32 and the graphite sheet 83 according to the present embodiment as viewed from the heater holder 31 side.

  As shown in FIG. 9A, in the present embodiment, after the graphite sheet 83 as the high thermal conductivity member is attached to the heater holder 31, the heater 32 is further attached. As a result, the longitudinal central portion of the heater 32 is supported by the heater holder 31 with the graphite sheet 83 interposed therebetween, and the longitudinal end of the heater 32 is supported in contact with the heater holder 31.

  The graphite sheet 83 is in the form of a sheet having a thickness of 0.2 mm, and as shown in FIG. 9B, the width in the longitudinal direction is 218 mm in length A and 214 mm in length B. It has a length relationship.

  The graphite sheet 83 is more flexible than when a metal is used as the high thermal conductivity member, so it easily adheres to the heater 32 during assembly, and the contact thermal resistance between the two tends to be low. Therefore, it is not necessary to apply grease to the contact surface of the two, and in this embodiment, no grease is applied to this position.

  In addition, the graphite sheet 83 is characterized in that its heat capacity is smaller than when a metal is used as the high thermal conductivity member. Therefore, there is an advantage that the temperature rise at the time of heating of the fixing device can be quickened. Furthermore, since the graphite sheet 83 improves the thermal conductivity in the sheet plane by orienting the graphite in the sheet plane, it is easier to obtain high thermal conductivity. The sheet used in this example has a thermal conductivity of 600 W / (m · K). The same material has different grade of orientation degree, and the thermal conductivity is different depending on the grade. A sheet having a further high thermal conductivity, such as a 1500 W / (m · K) sheet, may be used. Furthermore, "non-sheet-passing portion temperature rise" and "end portion offset" can be compatible at a high level. Moreover, compared with the case where an aluminum plate is used, there are restrictions of thickness (the grade of the thickness which distribute | circulates is few compared with aluminum), and a device is needed in an assembly | attachment and a holding method.

  The effects of using the present embodiment are the same as those of the first embodiment, so the description is omitted here.

  As described above, by adopting the configuration of this embodiment, it is possible to achieve both the suppression of temperature rise in the non-sheet-passing portion and the improvement in the fixing ability at the end portion at a higher level.

[Example 3]
In Examples 1 and 2, the present invention has been described using the longitudinal length A of the region a and the longitudinal length B of the region b of the high thermal conductivity member. This configuration is a configuration that can obtain the effects of the present invention at any of both longitudinal end portions of the image forming apparatus. In this embodiment, a configuration for obtaining an effect on at least one side (longitudinal one end side) will be described.

  As an example in which the present embodiment is effectively used, a description will be given using a configuration in which the reference of the transport (sheet passing) position is the one-side reference. The configuration of the image forming apparatus is the same as that of the first embodiment, as shown in FIG. The longitudinal section of the fixing device is the same as that of the first embodiment, as shown in FIG. Therefore, duplicate explanations are omitted.

  The positional relationship in the longitudinal direction of the aluminum plate 81 of the present embodiment different from the first embodiment will be described with reference to FIG. FIG. 10A is a view of the heater 32, the aluminum plate 81, the heater holder 31 and the like according to the present embodiment as viewed from the recording material conveyance direction. FIG. 10B is a schematic cross-sectional view of the heater 32 and the aluminum plate 81 according to the present embodiment as viewed from the heater holder 31 side. As shown in FIG. 10, in the present embodiment, the conveyance reference is on the right side in the drawing, and the right ends of LTR and A4 are at the same position. In this case, the temperature rise at the non-sheet-passing portion is not severe even if A4 is passed at the right side of the figure. Therefore, for the right side, it is easy to achieve both suppression of temperature rise in the non-sheet-passing portion and improvement in the fixing ability at the end. Therefore, in the present embodiment, any configuration may be used as long as the effect can be obtained only on the left side in the drawing.

  In order to obtain the effect with only one side, it is sufficient to consider the longitudinal length from the paper (recording material) standard. Here, description will be made using the distance from the center of the LTR sheet passing position to the left end (the end on the side where the effect is desired) of the aluminum plate 81 in the drawing. The configuration of the left end of the aluminum plate end 81 for obtaining the effect of the present embodiment is the same as that of the first embodiment. That is, the maximum longitudinal length from "LTR sheet passing area center" to "the left end of the contact area of the aluminum plate 81 with the heater 32" corresponding to the length A is 109 mm (the length of Example 1 Half of A). In addition, the maximum longitudinal length from “LTR sheet passing area center” to “left end of contact area of aluminum plate 81 with fixing film 30” corresponding to length B is 107 mm (Example 1 Half of the length B).

  On the other hand, the right side in the figure may have the configuration of Comparative Example 3 in which the end offset is OK. Accordingly, the maximum longitudinal length to the right end of the area a of the aluminum plate 81 is 107 mm, and the maximum longitudinal length to the right end of the area b of the aluminum plate 81 is 107 mm. Is 107 mm.

  As described above, by operating the configuration of the present embodiment, it is possible to achieve both the suppression of the temperature rise in the non-sheet-passing portion and the improvement in the end portion fixability at a higher level.

Example 4
In this embodiment, an example in which the present invention is applied in a configuration in which the length A of the aluminum plate used in the first embodiment is different will be described. The configuration of the image forming apparatus is the same as that of the first embodiment, as shown in FIG. The configuration of the fixing device is the same as that of the first embodiment, as shown in FIG. Therefore, duplicate explanations are omitted. The longitudinal positional relationship of the aluminum plate 81 of the present embodiment different from the first embodiment will be described with reference to FIG. FIG. 11A is a view of the heater 32, the aluminum plate 81, and the heater holder 31 according to the present embodiment as viewed from the recording material conveyance direction. FIG. 11B is a schematic cross-sectional view of the heater 32 and the aluminum plate 81 according to the present embodiment as viewed from the heater holder 31 side. In this embodiment, the length A of the aluminum plate is 219.5 mm, the length B is 214 mm, and the length A of the aluminum plate 81 is longer than the longitudinal length (219 mm) of the resistance heating element 82 of the heater 32. It is characterized by

  Hereinafter, the result of the image output experiment in the case of using the present embodiment will be described, and the effect in the present embodiment will be described. The configuration of the image forming apparatus and the basic configuration of the fixing device were the same as those of Example 1, and among them, those having conditions different only in the aluminum plate length were used. As an evaluation method, it evaluated using the evaluation method same as the evaluation method at the time of using Example 1. FIG. The evaluation results are as shown in Table 2.

  The results of Example 1 are as described in Example 1. In Example 4, the occurrence of the end offset did not occur (O), and the temperature rise at the non-sheet-passing portion was 221 ° C. . Further, the width of the area b of the aluminum plate 81 is 206 mm (image guaranteeing area) of the LTR (width about 216 mm) which is the recording material of the maximum width usable in the image forming apparatus of this embodiment. It is preferable to be longer than the left and right margins 5 mm). That is, the longitudinal end of the area b of the aluminum plate 81 is preferably outside the end of the largest image forming area in the longitudinal direction of the aluminum plate.

(Modification)
Hereinafter, modifications of the first to fourth embodiments will be described. In the first to fourth embodiments, the resistance heating elements 82 of the heater 32 are two patterns extending in the longitudinal direction, and the width (resistance value) in the lateral direction is equal along the longitudinal direction. I will not. Heaters that adjust the resistance of the resistance heating element 82 in the longitudinal direction to make the calorific value at the center and the end differ, and the heating ratio of the resistance heating elements of different lengths in the longitudinal direction independently or interlockingly It may be a heater capable of controlling the heat generation distribution of The resistance heating element may be a single pattern heater.

  The present invention has been described using the fixing device including the heater 32 in the first to fourth embodiments. However, similar effects can be obtained as long as the heater and the fixing film can be in contact with each other and the thermal conductivity of the high thermal conductivity member is higher than the base of the heater, such as a polyimide sheet heater, silicone rubber heater or sheathed heater. And the present invention can be applied.

  Further, in the first to fourth embodiments, the present invention has been described using the configuration in which the longitudinal length is A in the recording material conveyance direction with respect to the heater 32 and the region a of the high thermal conductivity member. However, the same effect can be obtained in a configuration in which the length A is not constant. An example is shown to Fig.12 (a)-(d). FIG. 12 is a view of the heater and the heat conducting member as viewed from the heater holder side. As shown in FIGS. 12A to 12D, the maximum longitudinal length A may be longer than B, and similar effects can be obtained.

  Further, the present invention has been described using the configuration in which the heater holder 31 in the first to fourth embodiments does not disturb the cylindrical shape of the fixing film 30. However, as shown in FIG. 13, the present invention can be applied to a configuration in which a protrusion is provided on the heater holder 31 so as to follow the R shape of the pressure roller 33.

  The present invention has been described using the longitudinal lengths A and B of the high heat transfer member in the fourth embodiment described above. This configuration can be applied to only one of the longitudinal ends of the image forming apparatus. As in the third embodiment, in order to obtain the effect with only one side, it is sufficient to consider the length in the width direction from the center of the paper (recording material) in the width direction. For example, it is assumed that the maximum width of the area a is A / 2 and the maximum width of the area b is B / 2 with reference to the LTR sheet passing center. The maximum longitudinal length of the heater 32 up to one end of the resistance heating element 82 relative to the LTR sheet passing center corresponding to them and the one end of the maximum image forming area (image guaranteeing area) of the maximum sheet passing width The maximum longitudinal length up to the part may be considered.

[Example 5]
The present embodiment differs from the first embodiment in the shape of the aluminum plate 81, but the other configuration is the same, so the description will be omitted. Details of the aluminum plate 81 of the present embodiment will be described.

  The positional relationship in the longitudinal direction of the aluminum plate 81 as the high thermal conductivity member of the present embodiment will be described with reference to FIG. FIG. 14A is a view of the heater 32, the aluminum plate 81, the heater holder 31 and the like according to the present embodiment as viewed from the recording material conveyance direction. FIG. 14B is a schematic cross-sectional view of the heater 32 and the aluminum plate 81 according to this embodiment as viewed from the heater holder 31 side. FIG. 14C is a schematic cross-sectional view of the vicinity of the fixing nip portion.

  As shown in FIG. 14A, in the present embodiment, after the aluminum plate 81 as the high thermal conductivity member is attached to the heater holder 31, the heater 32 is further attached. As a result, the longitudinal central portion of the heater 32 is supported by the heater holder 31 with the aluminum plate 81 interposed therebetween, and the longitudinal end of the heater 32 is supported in contact with the heater holder 31.

  The smaller the contact thermal resistance between the heater 32 and the aluminum plate 81, the better the thermal efficiency. Therefore, in the present embodiment, the above-described heat resistant grease is used in common, and the grease is interposed between the heater 32 and the aluminum plate 81.

  As shown in FIG. 14B, the substrate of the heater 32 of the present embodiment is a plate-like shape having a length in the longitudinal direction of 270 mm, a length in the lateral direction of 6.0 mm, and a thickness of 1.0 mm. The longitudinal length of the heat generating body 82 is 219 mm, and two patterns of the same resistance are formed.

  As shown in FIG. 14C, the aluminum plate 81 is bent in a Z shape so that the cross section becomes a hat shape. The portion of the aluminum plate 81 that hits the top crown of the cap is the area (portion) in contact with the heater 32. Here, this region (portion) is referred to as a region (heater contact portion) a, and a part of the portion corresponding to the hat-shaped eaves (boundary portion between eaves and slip) is an area (portion) in contact with the fixing film. This region (portion) is referred to as a region (film contact portion) b. In this embodiment, the longitudinal length B1 of the region b on the upstream side of the recording material conveyance direction of the portion corresponding to the eaves of the hat is 218 mm, and the length B2 of the downstream region b is 214 mm. Length (232 mm). The length B1 of the area b on the upstream side of the aluminum plate 81 is such that even if the LTR size paper (216 mm width), which is the recording material of the largest width, is conveyed with some variation, heat is conducted to the fixing film 30 up to the recording material end. In order to make it to be 218mm. Further, as shown in FIG. 14C, the region b on the upstream side of the aluminum plate 81 is more pressurized than the surface (first surface) of the heater 32 in contact with the fixing film 30 in the pressing direction of the nip portion. It is made to project to the roller 33 side. This is to prevent the staple from being caught on the upstream corner of the heater 32 and damaging the fixing film when the stapled recording material is passed through the recording material. The length B1 of the area b on the upstream side of the aluminum plate 81 is preferably wider than the width of the recording material having the maximum width, from the viewpoint of preventing breakage of the fixing film 30 due to stapling. On the other hand, the area b on the downstream side of the aluminum plate 81 has substantially the same height as the first surface of the heater 32 and there is no concern about the breakage of the fixing film 30 due to stapling. It is narrower than the width. By narrowing the longitudinal length B2 of the area b on the downstream side of the aluminum plate 81, the heat supply to the end of the fixing film 30 is slightly reduced, but it is possible to adjust by the length of the resistance heating element, etc. is there.

  Since heat of the second surface opposite to the first surface from the heater 32 can be supplied to the fixing film 30 through the aluminum plate 81, the heating efficiency of the fixing film 30 can be greatly improved. it can.

  However, at the longitudinal end of the contact area of the aluminum plate 81 with the fixing film 30, the metal edge and the inner surface of the fixing film 30 may be gradually scraped by sliding. In particular, when the positions of the edges of the longitudinal ends of the area b on the upstream side and the area b on the downstream side of the aluminum plate 81 are the same, both scrapes are added. Become. Therefore, in the present embodiment, the position of the edge of the longitudinal end of the area b on the upstream side of the aluminum plate 81 and the area b of the downstream side on the same side are made different. In addition, in order to reduce the internal surface scraping of the fixing film 30 due to the edge of the longitudinal end of the aluminum plate 81, the sagging side when punching out the shape of the aluminum plate 81 is the side in contact with the fixing film 30. Furthermore, processing such as polishing may be performed.

  Next, experimental results when this embodiment is used will be described. In order to verify the influence of internal surface scraping of the fixing film at the edge portion of the longitudinal direction end portion of the aluminum plate 81 in the configuration of the present embodiment, sheet passing durability was performed. A recording material having a basis weight of 75 g / m 2 and a paper size of Letter (largest size paper) was used as the recording material used for paper passage durability. In addition, as the sheet passing mode, the number of rotations of the fixing film is large, and the sheet is in the intermittent sheet passing mode where the fixing film is most severe for internal surface scraping. A surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd. : The scraped amount of the inner surface of the fixing film was measured by Surfcom 1500SD2). In the image forming apparatus used in the experiment, the process speed at this time is 200 mm / sec, the throughput is 40 sheets per minute in LTR longitudinal feed, and the apparatus life is 100,000 sheets. The atmosphere environment in which the experiment was conducted was a temperature of 23 ° C. and a humidity of 50%.

  The evaluation results are shown in Table 3. In the configuration of this embodiment, as described above, the length B1 of the region b on the upstream side of the aluminum plate 81 is 218 mm, the length B2 of the region b on the downstream side is 214 mm, and the ends of the aluminum plate 81 on the upstream and downstream sides The edge of the portion rubs at different positions on the inner surface of the fixing film. On the other hand, in the configuration of Comparative Example 5, the lengths of the upstream side and the downstream side of the aluminum plate 81 are both 218 mm, and in the longitudinal direction of the aluminum plate 81 It slides at substantially the same position on the inner surface of 30.

  The evaluation results are as shown in Table 3. In the configuration of the present embodiment, the amount of scraping of the inner surface of the fixing film is relatively small even when 100,000 sheets are passed, which is the lifetime of the apparatus.

  On the other hand, in the configuration of Comparative Example 5, the amount of scraping of the inner surface of the fixing film was twice that of this example due to the passage of 100,000 sheets of the lifetime of the fixing device. The length of the region b of the aluminum plate 81 shown in this embodiment is an example, and various configurations can be taken depending on the length of the resistance heating element 82 of the heater 32, the heat distribution, and the configuration of the pressure roller 33. It goes without saying that the same effect can be obtained by making the position of the edge portion of the longitudinal end of the aluminum plate 81 different on the upper and downstream sides of the fixing nip portion (the rotating direction of the fixing film 30).

  As described above, by making the position of the edge of the longitudinal end of the aluminum plate different on the upper and lower sides of the fixing nip portion, damage such as scraping of the inner surface of the fixing film can be reduced, and the long life and And a fixing device capable of high-speed printing can be provided.

[Example 6]
In this embodiment, a configuration is described in which the edge of the longitudinal end of the aluminum plate 81 as the high thermal conductivity member used in the fifth embodiment is formed obliquely with a predetermined angle as shown in FIG. Do. The configuration of the image forming apparatus is the same as that of the first embodiment, and redundant description will be omitted.

  The edge shape of the aluminum plate 81 as the high thermal conductivity member of the present embodiment will be described with reference to FIG. FIG. 15A is a view of the heater, the aluminum plate, the heater holder and the like according to the present embodiment as viewed from the transport direction. FIG.15 (b) is the figure which looked at the heater and the aluminum board which concern on a present Example from the heater holder side. Moreover, FIG.15 (c) is the figure which expanded the longitudinal edge part of the aluminum plate which concerns on a present Example.

  The characteristic of this embodiment is that, as shown in FIG. 15C, the edge of the longitudinal end of the area b of the aluminum plate 81 is inclined so that the upstream side is an angle α and the downstream side is an angle β with respect to the recording material conveyance direction. It is the structure currently formed. By this characteristic configuration, it is possible to disperse the portion rubbing against the inner surface of the fixing film 30 and the edge of the aluminum plate 81 and to reduce the scraping. The angles α and β may be about 5 ° to 85 °, more preferably 20 ° to 70 °. In this embodiment, a configuration example in which both the angles α and β are 60 ° will be described, but it is also possible to set different angles for the angles α and β.

  By forming the edge portion of the longitudinal direction end portion of the aluminum plate 81 in an oblique shape as in this embodiment, the temperature change of the fixing film 30 in the vicinity of the edge portion can be moderated, and the temperature rise of the end portion can be reduced. The effect is also obtained. The reduction effect of the non-sheet passing portion temperature rise will be described with reference to FIG. FIG. 16A is an enlarged view of the edge of the longitudinal end of the aluminum plate 81. The solid line in FIG. 16A is the shape of the present embodiment, and the broken line (the edge is a straight shape) is comparative example 6. FIGS. 16B and 16C are image diagrams of the temperature distribution in the longitudinal direction of the fixing film 30 when the LTR size recording material and the A4 size recording material are fixed. In the present embodiment, the area of the area b of the aluminum plate 81 in contact with the fixing film 30 is gradually reduced toward the outside in the longitudinal direction. Therefore, as indicated by solid lines in FIGS. 16B and 16C, the temperature of the fixing film 30 gradually changes toward the longitudinal end of the fixing film 30. On the other hand, in Comparative Example 6, as indicated by the broken lines in FIGS. 16B and 16C, the area of the region b of the aluminum plate 81 changes rapidly, so the temperature change of the fixing film 30 also changes rapidly. In order to keep the temperature of the fixing film 30 at a temperature that allows fixing to the longitudinal end, it is necessary to configure the configuration of Comparative Example 6 so that the temperature becomes high to the longitudinal end. From this, it can be seen that when the A4 sheet size recording material having a narrower width than the LTR size recording material is continuously fixed, the temperature rise in the non-sheet-passing portion is less aggravated in this example than in Comparative Example 6. .

  Next, experimental results when this embodiment is used will be described. In the configuration of the present embodiment, as described above, the edge of the aluminum plate 81 has an oblique shape (60 °), and the lengths of the upstream side and the downstream side of the aluminum plate 81 are 218 mm as the comparative example 6 A comparison was made with a configuration in which the edge of the part slides on substantially the same part of the fixing film 30.

  The evaluation results are as shown in Table 4. In the configuration of the present embodiment, the scraping amount on the inner surface of the fixing film 30 is small even if 100,000 sheets of paper passing (fixing process), which is the life of the fixing device, are performed. On the other hand, in Comparative Example 6, the scraped amount of the inner surface of the fixing film 30 is larger than that of Example 6 due to the passage of 100,000 sheets of the apparatus life.

  In the present embodiment, the configuration in which the aluminum plate 81 and the fixing film 30 are in contact in both the upstream and downstream areas of the fixing nip has been described, but only the upstream side of the fixing nip or only the downstream side The same effect can be obtained in the configuration in which the film 30 is in contact.

  Further, in the configuration of the present embodiment, since the edge of the longitudinal end of the contact area b of the aluminum plate 81 has an oblique shape, the technical difficulty in manufacturing is high in the bending process of the aluminum plate, and the parts cost Affects part accuracy. Therefore, it is desirable to select the configuration of the comparative example 6 (edge portion straight) or the configuration of the present embodiment (edge portion oblique shape) according to the characteristics such as the life and cost required of the device.

  As described above, by adopting the configuration of the present embodiment, damage such as abrasion of the inner surface of the fixing film can be reduced, and a long-life, high-speed printing fixing device can be provided.

[Example 7]
The image forming apparatus of this embodiment is the same as that of Embodiment 1 except that the process speed is 250 mm / sec, the throughput is 50 sheets per minute for LTR longitudinal feed, and the apparatus life is 300,000 sheets. I omit it.

  The edge shape of the aluminum plate 81 as the high thermal conductivity member of this embodiment will be described with reference to FIG. FIG. 17A is a view of the heater, the aluminum plate, the heater holder and the like according to the present embodiment as viewed from the recording material conveyance direction. FIG. 17B is a view of the heater and the aluminum plate according to the present embodiment as viewed from the heater holder side. FIG. 17C is an enlarged view of the longitudinal end of the aluminum plate.

  In this embodiment, as shown in FIG. 17C, the edge of the longitudinal end of the area b of the aluminum plate 81 in contact with the fixing film 30 has an angle α on the upstream side and an angle β on the downstream side with respect to the recording material conveyance direction. It is formed diagonally to become. By this, it is possible to disperse the rubbing portion at the inner surface of the fixing film 30 and the edge of the aluminum plate 81 and to reduce the scraping. Furthermore, by making the position of the edge of the aluminum plate 81 different on the upper and lower sides of the fixing gap portion, the rubbing portion on the inner surface of the fixing film 30 can be dispersed. The angles α and β may be about 5 ° to 85 °, more preferably 20 ° to 70 °. In the present embodiment, a configuration in which both the angles α and β are 40 ° will be described, but the angles α and β may be set to different angles. Further, in the present embodiment, the end edge on the upstream side of the aluminum plate 81 also slides in the forward direction with respect to the advancing direction of the fixing film 30, which is the best configuration for internal cutting of the fixing film 30.

  Next, experimental results when this embodiment is used will be described. In the configuration of the present embodiment, as described above, the edge of the region b of the aluminum plate 81 is formed in an oblique shape (40 °), and the position is made different at the upper and downstream of the fixing nip portion. The configuration of 6 was used. The evaluation method was compared in the same manner as in Example 1 above. The image forming apparatus used in the experiment has a process speed of 250 mm / sec, a throughput of 50 sheets per minute for LTR longitudinal feed, and an apparatus life of 300,000 sheets.

  The evaluation results are as shown in Table 5. In the configuration of the present embodiment, the scraped amount of the inner surface of the fixing film 30 is smaller than that of the comparative example 7 even if 300,000 sheets of paper, which is the life of the apparatus, are passed. However, although the configuration of the comparative example 7 is inferior to the configuration of the present embodiment with respect to the device life, it is superior to the present embodiment with respect to the effect of suppressing the non-sheet-passing portion temperature rise. Is desirable.

  Further, as a modification of the present embodiment, it is confirmed that the scraping reduction effect of the inner surface of the fixing film 30 is also obtained in the configuration as shown in FIG. However, since the edge of the longitudinal end on the upstream side of the aluminum plate 81 slides in the counter direction with respect to the advancing direction of the fixing film 30, the internal film reduction effect of the fixing film 30 is lower than that of this embodiment. However, since the manufacturing difficulty is lower in the configuration shown in FIG. 18 (the width of the tip is wider than the base of the bending of the aluminum plate), which configuration is required according to the required characteristics such as cost / precision of the device It is desirable to choose.

  As described above, by adopting the configuration of this embodiment, damage such as abrasion of the inner surface of the fixing film 30 can be reduced, and a long-life, high-speed printable fixing device can be provided. .

12 fixing device 30 fixing film 32 heater 33 pressure roller 81 aluminum plate 83 graphite sheet a heater contact portion b aluminum plate contact portion P recording material t toner image

Claims (5)

A rotatable tubular film,
A plate-like heater having a first surface and a second surface opposite to the first surface, the long thin plate heater contacting the inner surface of the film on the first surface;
A heat conducting member having a heater contact portion which is long in the longitudinal direction of the heater and is in contact with the second surface of the heater;
A fixing device that heats a toner image by the heat of the heater through the film and fixes the toner image on a recording material;
The heat conducting member extends in a direction approaching the film in at least one of a region upstream of the upstream end of the heater and a region downstream of the downstream end of the heater in the rotational direction of the film. A film contact portion contacting the inner surface of the
A fixing device, wherein a longitudinal end of the heater contact portion extends outward beyond a longitudinal end of the film contact portion on the same side in the longitudinal direction of the heat conducting member.   The film contact portion is a first film contact portion provided in a region upstream of the upstream end of the heater, and a second film contact portion provided in a region of the downstream end of the heater. The fixing device according to claim 1, further comprising:   The longitudinal end of the first film contact portion is different from the longitudinal end of the second film contact portion on the same side in the longitudinal direction of the heat conducting member. Fixing device.   The fixing according to claim 3, wherein the longitudinal end of the first film contact portion extends outward beyond the longitudinal end of the second film contact portion in the longitudinal direction of the heat conducting member. apparatus.   The roller according to any one of claims 1 to 4, further comprising: a roller forming a nip with the heater through the film, wherein the recording material on which the toner image is formed is conveyed and heated in the nip. The fixing device according to claim 1.

Images